If you really want your flowers and vegetables to do well, you should know your soil pH so that you can add whatever is needed to get it to the right level for each plant type.

What is pH?

If you remember chemistry lessons from school, you might remember testing different substances with a bit of litmus paper to see what colour it turns, indicating if the substance is acid or alkaline. Well, soil in different areas has different levels of acidity. Some plants prefer alkaline soil, while others will thrive in a slightly acid situation. It’s important to know what your soil type is so that you can plant the best suited plants, or use additives to ensure other plants will thrive.

pH is measured in numbers. A pH value of 7.0 is neutral – neither acid or alkaline. Anything above 7.0 is alkaline, while anything below 7.0 is acid. The further away from 7.0 you go, the more acid or alkaline the soil is.

Generally you can assume that if you live in a soft water area, your soil is likely to be acid, while if you have hard water your soil is more likely to be alkaline. Another way to guess the pH is by soil type – peaty soil is usually acid. If you have clay soil it probably neutral, or if your soil is chalky it will be alkaline.

Testing Your Soil

You can try taking a guess at your soil levels, but it’s best to do a test to know for sure. You can buy a soil testing kit from a garden centre. The kits are fairly cheap, so it is a good idea to buy two so that you can be sure of the result.

Once you’ve got your testing kit, follow the instructions carefully. It’s a good idea to take soil from several parts of the garden and mix it together, unless you are testing the pH of one specific area.

What the Results Mean

If it turns out you have acidic, or ericaceous soil, you can successfully grow lime-hating plants such as rhododendrons, camellias, azaleas and heathers.

If you have neutral soil, you should be able to grow most plants successfully, except the lime-hating plants mentioned above.

If your soil is alkaline then you’re less fortunate. There is one group of plants that will do well in alkaline soil, and that is wildflowers. Poppies, chamomile and cornflower are all flowers that should thrive in alkaline soil, and herbs such as bay, lavender and rosemary will also do well.

You can change the level of your soil on a small scale – if you have acid soil you might add lime to a patch where you are growing brassicas, or if you have alkaline soil you can mix in lots of well-rotted manure to improve it. However, to try and change your whole garden is an expensive and time-consuming undertaking that just isn’t worth it. Instead, embrace the plants that will like your soil, and grow the ones that won’t in pots or raised beds.

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